


Alpha

by daemonhart



Category: Undertale (Video Game)
Genre: Alpha/Beta/Omega Dynamics, Anal Sex, Incest, Knotting, M/M, Mating Cycles/In Heat, Mpreg, Plot What Plot/Porn Without Plot, Sibling Incest
Language: English
Status: Completed
Published: 2018-02-12
Updated: 2018-02-12
Packaged: 2019-03-17 06:15:30
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 468
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13653144
Author URL: https://archiveofourown.org/users/daemonhart/pseuds/daemonhart
Summary: [Drabble] A request for MPREG from an anon on my tumblr! Papyrus is a handful on a normal day, but when rut hits, he gets to business.





	Alpha

**Author's Note:**

> This was a response to a request! Of course, I'm always looking for more reasons to write cumshots and knotting...

“fuck…! ngh, bro! hah! ah~! s-so damned close…” Sans’ fingertips dug hard into rug beneath him. Slick magical fluids dripped from his pelvis in long, sticky threads to the floor and seeped in, leaving behind a damp spot. Every time his brother’s gradually-swelling knot popped past his ring of ectoplasmic muscle, he gave another encouraging moan. “i need~ it…c’mon, paps…fuckin’ do it!”

Papyrus growled and latched his hands onto the smaller monster’s ilia. Rut was enough to drive even a docile creature like him into breeding his sibling raw. The extra leverage allowed him to pound as hard as he liked, with their bones clacking sharply every time he hilted himself. Sans could feel the bulb of his cock struggling to pass into his hole. It hurt at first, but the intense high of being claimed by such a strong male distorted every painful jolt and seemed to send it straight to his dick. His tongue lolled free from his open, panting jaws. The sudden snap of teeth around his spine made him arch his back down and present himself. This was it. One last time, Papyrus’ knot forced inside.

Sans struggled to breathe under the onslaught of short, hard thrusts that followed. His words of encouragement fell away into desperate moans. Every violent shove served to seat Papyrus’ cock deeper into his receptive mate. Pleasure was secondary to his need to fill a fertile monster, but for his breeder, the rush of sex served as a reward. In return, Sans needed only to offer his brother, his _alpha_ the chance to create young. Every thrust rubbed him deep until suddenly, a buzzing sense of euphoria roared in his skull. “oh…! ah, yeah~ yesss…!” His glowing semen spattered against the carpet and his conjured ass tightened around the nearly softball-sized knot. In turn, Papyrus snarled against his bones. Long arms lifted and locked around Sans’ ribs while pulse after pulse of the rutting monster’s load swelled the filled space. A quick tug tested that the tie was complete; not a drop of seed would be wasted. The pull earned an appreciative hiss from his partner. Nothing was as satisfying as a thick knot plugging him up.

The tightening of Papyrus’ bite rolled Sans’ pupils back and milked a delirious groan from his mouth. More! More~ Satisfaction shuddered through his bones once a film began to form between his ribs and pelvis, then wrapped around to his spine. Once the space closed, he felt a tiny flicker of warmth within himself – success. In the near future, Papyrus would be a sire. For now, though…Sans managed to glance over his shoulder at his senseless mate when the mating bite released. This rut was only beginning. He still had a few days longer to enjoy getting fucked silly.


End file.
